Immanuel Rath, an old bachelor, is a professor at the town's university. When he discovers that some of his pupils often go into a speakeasy, The Blue Angel, to visit a dancer, Lola Lola, he comes there to confront them. But he is attracted to Lola. The next night he comes again--and does not sleep at home. This causes trouble at work and his life takes a downward spiral.
You can find out more about this movie on its IMDB page.